Medical procedures often require locating and treating target areas within a patient. In some procedures, it is important to locate the target with a high degree of precision to limit damaging healthy tissue surrounding the target. For example, it is particularly important to know or be able accurately to estimate the precise location of the target in radiation oncology because it is desirable to limit the exposure of adjacent body parts to the radiation in a patient already suffering the depredations of cancer. However, in all treatment procedures, whether radiologic or otherwise, it is most desirable to be able to accurately target a region to be treated in a manner that protects the tissue and organs immediately surrounding the target location.
In many applications, it is not possible to directly view a treatment target or portion thereof (such as, for example, a cancerous tumor, cyst, pseudocyst, or other target) that needs to be acted on in some manner (e.g., biopsy, excision, etc.). It is therefore highly advantageous to have some mechanism for permitting the target to be located accurately so that the procedure can be carried out in an accurate and precise manner while avoiding damage to healthy tissue.
Even for target regions that may be visualized using CAT (computer-assisted tomography) scans, MRI (magnetic resonance imaging), x-rays, ultrasound, or other techniques, difficulties often arise in targeting a treatment. This is particularly true for target regions within a torso of a patient and soft tissue regions. Due to the mobility of tissues in those regions (e.g., movement of internal organs during respiration and/or digestion, the movement of breast tissue with any change of body position, etc.), a target region may not remain fixed relative to anatomical landmarks and/or to marks that can be placed onto an external surface of a patient's body during one of those visualization procedures.
Several techniques have been developed to address this problem. One such technique is to place markers into the patient along the margins of the target region. The markers may be active (e.g., emitting a signal useful in targeting a therapy) or passive (e.g., fiducial markers) that can be used for targeting under ultrasound, MRI, x-ray, or other targeting techniques.
For the purposes of creating targets for medical imaging, fiducial markers (e.g., hereinafter referred to as “fiducials”) are small implants that are placed within the body cavity and give medical imaging systems permanent or semi-permanent targets for imaging and diagnosis. A fiducial is generally formed of a radio-opaque material and placed adjacent to a target site so that the target can be effectively located and treated with a device that targets a site using the fiducials as positional markers under radiographic detection. The placement of more than a single fiducial is generally desirable, as it allows for imaging systems to more accurately determine the location of a specific tissue based on multiple fiducials surrounding the tissue, which results in a more accurate orientation of targeted visualization. For example, in some instances, the placement of three fiducials is desirable, as it allows for imaging systems to more accurately triangulate and determine the location of the specific tissue and provide a three-dimensional orientation of targeted visualization.
Generally, fiducials are placed and positioned within a patient's body via percutaneous placement procedures utilizing the traditional “stylet-push” method. The traditional stylet-push procedure generally consists of a catheter having an internal lumen, where one or more fiducials are loaded within. The fiducials are then pushed out of the catheter by advancing a stylet through the catheter lumen, thereby driving the fiducials out of a distal end the catheter and into the desired location.
FIGS. 1 and 2 are provided to illustrate one embodiment a two-piece introducer 10 currently available for use in placement of fiducials via the stylet-push method. Referring FIG. 1, the introducer 10 includes a needle 12 and a stylet 14 slidably disposed within the needle 12. The stylet 14 includes a first handle 15 and a blunt distal end 16. The needle 12 includes a second handle 13 and a bevel-tipped cannula 18 extending through the second handle 13. The cannula 18 is configured to hold a fiducial 20 within. The cannula 18 has a distal tip 19 configured for percutaneous implantation of the fiducial 20 into the patient.
In a pre-loaded configuration, as shown in FIG. 1, the fiducial 20 may be retained within the cannula 18 by a plug 22 made from bone wax or other suitable bio-compatible material(s). This is typically accomplished by a “muzzle-loading” technique where the fiducial 20 is placed into the distal end 19 of the needle 12 and then held in place by the bone wax plug. This can present some challenges, as the bone wax plug 22 can be visible as an artifact in the patient, potentially interfering with clear visualization of body structures or treatment devices. With this configuration, the cannula 18 must be withdrawn and reloaded after delivery of each fiducial 20. If the target locations for the fiducials are very far apart, use of a single percutaneous introducer cannula/trocar for multiple introductions of the cannula 18 may not be possible. In such a circumstance, the patient must endure several percutaneous punctures, and further endure the increased attendant risk of infection for each, including inadvertent puncturing or trauma to surrounding tissue.
In order to implant a fiducial 20 at a target location in a patient, a clinician first pushes the cannula 18 in a first direction, as indicated by arrow A, so as to insert the tip 19 into the patient (typically under fluoroscopic visualization). The clinician then pushes the second handle 13 further in the first direction to position the tip 19 at the desired depth within the patient where a fiducial 20 is to be implanted. Throughout this motion, the clinician moves the needle 12 and the stylet 14 together as a unit. At the desired depth/location, the clinician grasps the first handle 15 with one hand and the second handle 13 with the other hand. Then, the clinician holds the first handle 15 stationary while simultaneously sliding the second handle 13 back in a second direction, as indicated by arrow B, toward the first handle 15. As shown in FIG. 2, this movement causes the cannula 18 to retract over the fiducial 20 resulting in implantation of the fiducial 20 into the patient. Alternatively, the clinician may move the first handle 15 in the first direction while sliding the second handle 13 back in the second direction or holding it stationary, thereby causing the stylet 14 to push the fiducial 20 out of the cannula 18. The procedure is then repeated to place other fiducials.
As will be appreciated from the disclosed structure, after deploying one fiducial, a clinician may reload the introducer 10 from the proximal end by completely withdrawing the stylet 14, then placing another fiducial into the needle lumen and advancing it therethrough to a second location to which the distal needle tip 19 has been directed (a “breech-loading” technique). However, having to withdraw and reload takes up valuable time and complicates the procedure, potentially requiring additional personnel, whether only the stylet is withdrawn for “breech-loading” or the entire device is withdrawn for “muzzle-loading.” Furthermore, due to the withdrawing and reloading of current deployment devices, multiple percutaneous punctures are subsequently required when deploying additional fiducials to the target site, which, in turn, may result in inconsistent and/or inaccurate placement of fiducials, as well as an increased risk of trauma to surrounding tissue, increasing the risk of harm to the patient. Additionally, in some anatomies, such as the liver and pancreas, the long access length and tortuous anatomy can make it difficult to deploy fiducials using the traditional stylet-push method. As such, clinicians may find it difficult to deploy multiple fiducials in an accurate and consistent manner.